Action of estradiol and tamoxifen on the Müllero-regressive activity of the chick embryonic testis assayed in vivo by organotypic grafting

R. Stoll, F. Ichas, N. Faucounau, R. Maraud
Anat Embryol. 1993-04-01; 187(4):
DOI: 10.1007/bf00185896

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In the chick, the implantation of a testis graft from a 13-day-old male donor
embryo into the extra-embryonic coelom of 3-day-old female embryos induces the
total regression of their Müllerian ducts because of the anti-Müllerian hormone
(AMH or MIS) secreted by the implant. Pre-treatment of the donors with estradiol
(E2), between day 12 and day 13, counteracts in a significant way the
Müllero-regressive activity of the implant. Co-treatment of donors at the same
stage with both Tamoxifen (TAM) and E2 restores the initially observed activity,
thus demonstrating the presence of Tamoxifen-sensitive estrogen receptors at the
late stage of treatment in the Sertoli cells responsible for AMH secretion. The
treatment of 3-day-old male donor embryos with E2 causes the differentiation of
their left gonad into an ovotestis which provides implants totally devoid of
Müllero-regressive activity. The additional treatment with TAM of the grafted
host embryos, does not modify the results obtained when E2-treated male gonads
are grafted to host embryos not treated with TAM. This shows that the lack of
Müllero-regressive activity exhibited by the E2-treated male gonads does not
depend on the estrogens they may secrete during the time of the assay, i.e., it
cannot be attributed to a protecting action of estrogens on the MDs of the host.
Our results therefore favor the idea that E2 down-regulates AMH. The relevance of
such a regulation to the phenomenon of Müllerian duct maintenance, either in the
E2-feminized male or in the female chick embryo, is discussed.

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